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Title: A Post Mortem Study of Otters (Lutra Lutra) Found Dead in South West England
Author: R Simpson V
Author: Environment Agency
Document Type: Monograph
Annotation: Environment Agency Project ID:EAPRJOUT_291, Representation ID: 60, Object ID: 1637
OF MAIN FINDINGS 1. Postmortem examinations were carried out on77~otters between December l988 and March 1996. With the exception of two cases from Hampshire,. all the otters came from Cornwall, Devon and Somerset. None were received from-Dorset:,.Wiltshire or South Gloucestershire. 2. The numbers submitted increased noticeably from 1992. In part; this was due to increased submissions from NRA/Agency.staff. From 1993 to 1996, twice as-many males as females.were submitted.. a. 3.: There was-a marked pattern of seasonal.mortality, with-very few deaths in the summer months. Female mortality peaked in February-and male March and December. Seasonality in mortality may be influenced by rainfall patterns, with otters frequently killed on roads a day or so after periods of heavy rain ,when rivers are in spate. Such rainfall events most commonly occur between September and.March. 4: Road traffic accidents were responsible for 83 % of mortality. Bite wounds,- apparently caused by other otters; were seen in 12 animals (16 %), and five died as a result of their injuries. 5.a On average,-males were larger than females but they were in overall poorer condition. There was no evidence of deaths due to starvation. Ia 6. Dental condition was generally. good. Examination of two years for both males and females.: 7. of teeth from 28 animals indicated a mean age Very few gross pathological lesions were seen, indicating a general absence of significant bacterial, viral or parasitic diseases. Streptococcal infections ,were seen in animalsasuffering from bite wounds. 8. Occasional focal lesions were seen in lungs and were mostly due to inhaled fungalspores. Some lesions resembled tuberculous foci; but specific stains showed no evidence of mycobacteria. Sarcocystis infection was seen in the external eye muscles of one otter. .. 9. Adrenal hypertrophy and splenic atrophy were seen in males. dying of bite wounds; Enlarged adrenal glands were also seen in females in late pregnancy and early lactation. There was a separate; strong; positive correlation between adrenal.weight and liver PCB levels,, particularly for congeners 138,153 and 180. 10. Evidence of reproduction was seen in 11 out-of 25 female otters, with two being pregnant and four lactating. 11. Three otters, one of which was in-early pregnancy, had convoluted uteri. Although these appeared abnormal-.their significance is uncertain; One stunted male: was a cryptorchid with a single, undescended testis and histological examination showed no spermatogenesis in either testis. 12. Samples of ,liver were analysed for a wide range of organic -pollutants and for heavy .metals. The liver levels of PCBs, Dieldrin and ppa DDE .were generally higher in males than females, although this only achieved significance in the case of PCBs. R and D Technical Report W148 V 13. There was a relationship between pollutant levels and body weight, with higher levels in heavier animals. There was also a -positive correlation between thyroid weight and body weight, but no significant connection between thyroid weight and pollutant levels after the relationship with body weight had been taken into account. 14. The heavy metal concentrations in most cases were considered to be of little or no significance. One otter from Hampshire had an elevated arsenic level. Mercury levels were generally low but, as this metal accumulates with age, these levels could be a reflection of the young age of the animals in this study. 15. PCB levels were mostly lower than those reported in previous studies but some animals had levels which were considered to be high. The results show a significant decline in the concentration of congeners, 118, 138, 153, and 180, but not of total PCB, over the period of the study. 16. Two otters had high Dieldrin levels. One came from Newbridge, west Cornwall, where very high levels had been reported in eels two years previously. The source was believed to have been Aldrin used on daffodil crops. The second animal came from near Falmouth, Cornwall but in this case no source was apparent. Dieldrin levels declined significantly between 1988 and 1996. 17. DDT levels were considered to be low in the majority of animals but, as with Dieldrin, the results show a significant decline over the period of the study. The levels of yHCH were all low but also declined significantly. There were no significant residues of other organochlorine pesticides, organophosphates or herbicides. 18. Analysis of liver samples for Vitamin A content showed a wide range of values. Seven animals had less than 7 pmol/kg and in most species this is considered to be evidence of deficiency. Five animals had values of around 1,000 pmollkg or more. 19. Very low Vitamin A levels were typically seen in animals which also had high levels of PCBs, Dieldrin and DDT. Although the results provide evidence of an inverse relationship between Vitamin A and some of these pollutants, a causal connection was not demonstrated. 20. Most of these animals with low Vitamin A levels and high PCB and OC levels were seen in the period 1988-1992. 21. Gonadal hypoplasia and cryptorchidism are recognised features of Vitamin A deficiency, and the Vitamin A level in the cryptorchid otter in this study was below the limit of detection. Apart from this case, no other otter had gross lesions indicative of Vitamin A deficiency. 22. Histopathological examination of livers showed bile duct hyperplasia and fibrosis of varying degree in almost all the otters. In most animals the thyroid glands had small or very small follicles with sparse, pale staining, colloid. In some cases there was little or no colloid and the glands appeared very vascular. In others the follicles were well developed and full of pink staining colloid. Splenic atrophy and adrenal cortical nodular hyperplasia were seen in several otters. Although these observations may be related to the levels of pollutants present, too little is known about the normal appearance of these tissues in otters to draw definite conclusions. No specific lesions of Vitamin A deficiency were seen. R and D Technical Report W148 vi ACKNOWLEDGMENTS The author wishes to thank the many people who contributed to this project, in particular, Lyn Jenkins, Mike Williams, Sonia Thurley, Martin.Rule, Rachel Brown, Bruce Brown and Lee Eckford- of the Environment Agency..He is also grateful to the Environment Agency for.funding the contract and to the Joint Nature Conservation Committee for additional financial support-Thanks go to Les Sutton and Rex Harper of the RSPCA, Hilary~Marshall, James Williams, Graham Roberts, David, Curtis and members of the Cornwall Wildlife Trust, who regularly submitted carcases.:Drs. Hans Kruuk and Jim Conroy, ITE, kindly examined teeth; John Jones, Irene Bryant and Jane Archer assisted with the figures and LindsayaDannatt examined the snared..otter. The author is most grateful to Mike Bain .and colleagues for performing the Vitamin A estimations, to Alan Hunt for valuable advice on biochemistry and to Ranald-Munro and Dolores Gavier-Widen for advice on histopathology. The staff at the Central Veterinary Laboratory library were most helpful in .providing .references and Brian Preece made constructive comments on the draft manuscript.,Particular thanks goto Bob Lacey, WRc, who not only carried out the statistical analysis, but also suggested improvements,to the manuscript:Finally; thanks go to the Polwhele VI Centre for constant technical support and Lyn Penrose for typing the manuscript.. R and D Technical, Report.Wl48 vii 1a
Publisher: Environment Agency
Subject Keywords: Toxicological testing; Otter
Extent: 91
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